The application claims priority to German Patent Application No. 10042425.2, filed Aug. 28, 2000.
This invention concerns a roller cage which is part of a tool designed for deep rolling of grooves on crankshaft journals or crank pins. Such a tool is known in the art, for example, from EP 0 839 607 A1. The roller cage is guided at the end of an L-shaped tool holder.
Work rollers are known in the art, for example, from U.S. Pat. No. 5,806,184. Two work rollers are guided inside each of the roller cages and inclined at an angle. The slope is selected so that the sections of the work rollers guided inside the roller cage have a smaller distance from the longitudinal center of the deep rolling tool than those sections of the work rollers that are located outside the roller cages.
The physical roller cage has rather small dimensions. Its base area is, for example, only 10 to 30 mm wide and 10 to 15 mm long. The height of the prismatic base body is between 8 and 15 mm. These dimensions apply to a tool appropriate for the processing of crankshafts for passenger car engines.
The work rollers are made of hardened steel while the roller cages consist of bronze which, along with minimal wear, has especially favorable sliding characteristics. But other materials may also be considered for the roller cage, such as titanium or ceramics.
Nevertheless, roller cages are subject to a high level of wear which results in their relatively short tool life. With progressive wear of the roller cages, however, work rollers are also subject to wear. This stress pattern eventually requires roller cages and work rollers always to be replaced at the same time, when wear on the roller cage alone has reached a certain extent.
The object of this invention calls for an increase in the useful life of a roller cage to achieve an increase in the service life of the deep rolling tool as a unit, yet using one and the same work roller.
It was found that this object may be attained by providing a minimum of one second concave recess identical in position and size to the first concave recess, on the second face of the prismatic body opposite the first concave recess, for guiding the work roller.
When wear of the first concave recess for guiding the work roller has reached a certain depth, the roller cage is reversed within the tool, and the work roller with then be guided in the second concave recess provided on the rear face of the roller cage until the permissible level of wear is reached there also. The result is the improved utilization of the roller cage. Due to its small dimensions, the required precision and its multiple machining operations, such a roller cage represents a highly complex component of the tool whose manufacturing costs are high, accordingly. Due to the improved utilization of this component based on the invention, the overall economy of the deep rolling tool can be increased.
As shown in the above mentioned state of the art, it is customary to guide two work rollers inside of one single roller cage simultaneously. This arrangement applies to crankshafts on which each journal is followed by one crank pin. With crankshafts having two adjacent crank pins, though, the so-called split crankshafts, it is also customary to operate with only one single work roller inside one roller cage. This invention is to cover these applications also. For this purpose the first and second concave recess on the first and second face of the prismatic body are provided as mirror images of each other relative to the body""s longitudinal center.
On the external end of the L-shaped tool holder each roller cage is guided in a tongue shaped extension of the tool holder. This tongue shaped extension engages a longitudinal groove of the prismatic body of the roller cage so as to provide the bottom of the entire deep rolling tool with a plain edge from which only the non-guided sections of the work rollers protrude. The engagement between the roller cage and the L-shaped tool holder requires the longitudinal groove inside the roller cage to have a certain slope. Since in the case at hand the roller cage is to be utilized from both faces, design provisions call for the slope to drop toward both face areas of the roller cage. With the help of these means, a particularly simple and effective roller cage mount is accomplished.